How much money do I need to start investing?

Less than you think. A lot less. Most big brokers have no account minimum, and since fractional shares became standard you can buy a slice of a $900 stock for $5. The old idea that you need a few thousand dollars to "get started properly" died a few years ago and nobody told the general public.

The more useful question is how much you can invest regularly without feeling it. Someone putting in $25 every payday will end up in a far better place than someone who saves up $3,000, invests it once, and never adds another cent. Regular beats big.

There are two things worth having in place first: a small cash buffer for surprises, and no credit-card debt at 20-plus percent interest, because no investment reliably beats that. Beyond those, waiting until you have "enough" mostly costs you years of growth.

If you want a number to aim for, many people start with $100 to get comfortable with how the account works, then switch on an automatic monthly transfer. The starting amount is a rounding error over a lifetime; the monthly amount is not.